LONG-SIMMERING tensions between the Bush Administration and the United Nations leadership erupted into open warfare yesterday when Washingtonâs ambassador voiced outrage at criticism of the United States by the UNâs British second-in-command.

John Bolton, the US Ambassador to the UN, called on Kofi Annan, its Secretary- General, to âpersonally and publicly repudiateâ criticisms of the US and its people by Mark Malloch Brown, his British deputy.

But Mr Annan, an old friend of Mr Malloch Brown who has promoted him to a series of top jobs in the UN system, retires on December 31 after a decade in office and was in no mood to back down.

âThe Secretary-General stands by the Deputy Secretary-General and agrees with the thrust of his speech,â Mr Annanâs spokesman said last night. âThe speech was not a mistake.â

In his speech on Tuesday, Mr Malloch Brown attacked the US for âtoo much unchecked UN-bashing and stereotyping over too many years. From Lebanon and Afghanistan to Syria, Iran and the Palestinian issue, the US is constructively engaged with the UN,â he said.

âBut that is not well known or understood, in part because much of the public discourse that reaches the US heartland has been largely abandoned to its loudest detractors, such as Rush Limbaugh and Fox News,â he added.

âThat is what I mean by âstealthâ diplomacy: The UNâs role is in effect a secret in Middle America even as it is highlighted in the Middle East and other parts of the world.â

Mr Bolton told Mr Annan that Mr Malloch Brownâs comments were âthe worst mistake by a senior UN officialâ that he had seen in many years and would damage the world body.

Analysts say that the clash could imperil congressional funding for the UN. The US, which pays 22 per cent of the UNâs administrative budget, is already threatening to block its budget for the second half of this year unless it adopts a set of management reforms.